+ Post New Thread
Results 1 to 5 of 5
  1. #1
    Full Member level 4
    Points: 1,318, Level: 8

    Join Date
    Jan 2018
    Posts
    219
    Helped
    1 / 1
    Points
    1,318
    Level
    8

    What is the effect of power match on S11 and S22 in a PA

    Hi, by using conjugate matching it is possible to achieve maximum power transfer and also the good input and output matching. But in case of PA, sometimes we are delibarately creating mismatch. How does this effect the S11 and S22, and what kind of measures should be considered to get a good matching while getting a power matching condition also.

    One way,I think, is that the output impedance of the active device and required optimum load should be as close as possible, so that that mismatch can be reduced, correct? any other?

    •   AltAdvertisement

        
       

  2. #2
    Advanced Member level 5
    Points: 17,262, Level: 31
    pancho_hideboo's Avatar
    Join Date
    Oct 2006
    Location
    Real Homeless
    Posts
    2,662
    Helped
    714 / 714
    Points
    17,262
    Level
    31

    Re: What is the effect of power match on S11 and S22 in a PA

    Quote Originally Posted by circuitslave View Post
    by using conjugate matching
    it is possible to achieve maximum power transfer
    and also the good input and output matching.
    What do you want to mean by "good" ?

    Quote Originally Posted by circuitslave View Post
    But in case of PA, sometimes we are delibarately creating mismatch.
    What do you want to mean ?

    Quote Originally Posted by circuitslave View Post
    How does this effect the S11 and S22,
    and what kind of measures should be considered to get a good matching
    while getting a power matching condition also.
    What do you want to mean by "good" ?

    Quote Originally Posted by circuitslave View Post
    the output impedance of the active device and required optimum load should be as close as possible, so that that mismatch can be reduced, correct?
    Wrong.

    Can you understand operation class of PA ?
    There are many operation class for PA, class-A, class-C, class-D, class-E, classs-F, class-S, etc.

    Even if your PA is class-A, best low distortion is achieved at mismatch condition.
    If your PA is for modulated signal, impedance issue will be more complex.

    Surely learn very basic things before EDA Tool Play.
    Last edited by pancho_hideboo; 22nd October 2019 at 15:37.



    •   AltAdvertisement

        
       

  3. #3
    Member level 5
    Points: 711, Level: 5

    Join Date
    Aug 2018
    Posts
    92
    Helped
    25 / 25
    Points
    711
    Level
    5

    Re: What is the effect of power match on S11 and S22 in a PA

    S-parameter works fine only for small signal. For PA, s-parameters vary with power level, so X-parameters are used instead. For PA design, efficiency and distortion are more important factors than S11 and S22. Load-pull method is used for PA impedance matching. If you really care about reflection, 90 degrees hybrid combiner could be used to reduce reflection at both input and output ports.
    Click image for larger version. 

Name:	bybrid_combiner_PA.PNG 
Views:	4 
Size:	17.3 KB 
ID:	156162


    1 members found this post helpful.

    •   AltAdvertisement

        
       

  4. #4
    Full Member level 4
    Points: 1,449, Level: 8

    Join Date
    Jan 2019
    Location
    Ireland
    Posts
    206
    Helped
    86 / 86
    Points
    1,449
    Level
    8

    Re: What is the effect of power match on S11 and S22 in a PA

    Whether to use conjugate match or power match at the output
    Please refer to the figure below
    Click image for larger version. 

Name:	power_match_vs_conjugate_match.JPG 
Views:	6 
Size:	92.9 KB 
ID:	156169
    *Lets ignore the reactive part for now
    One can immediately see the problem if the output is conjugately
    matched. As seen in figure above, for a gain match, the output current swing is quite
    small and therefore the available power will be quiet small. On the other hand, if the
    real part of the load line is selected as shown by the green line in figure, a larger
    output current swing is available, and therefore a larger power output is available.
    This is referred to as power matching
    What type of matching to do at the input
    Conjugate match.
    I typically run a large signal s-parameter simulation and find the input impedance at the power level where I am most concerned about. I design my input matching to match at that point.
    .


    1 members found this post helpful.

  5. #5
    Full Member level 4
    Points: 1,318, Level: 8

    Join Date
    Jan 2018
    Posts
    219
    Helped
    1 / 1
    Points
    1,318
    Level
    8

    Re: What is the effect of power match on S11 and S22 in a PA

    Quote Originally Posted by circuitking View Post
    Hi, by using conjugate matching it is possible to achieve maximum power transfer and also the good input and output matching. But in case of PA, sometimes we are delibarately creating mismatch. How does this effect the S11 and S22, and what kind of measures should be considered to get a good matching while getting a power matching condition also.

    One way,I think, is that the output impedance of the active device and required optimum load should be as close as possible, so that that mismatch can be reduced, correct? any other?
    I found this in book Wireless Communications Circuits and Systems, By Institution of Electrical Engineers
    Click image for larger version. 

Name:	Refl_PA.PNG 
Views:	10 
Size:	39.0 KB 
ID:	156200



--[[ ]]--